The main type of soccer training which can be carried out by a person practising on their own relates to ball control skills, where the ball is kept under close control with the feet and/or the head, and it is widely acknowledged that this type of training is very useful in developing soccer skills.
Carrying out such practice on one's own can however be frustrating, particularly for those less skilled because if the ball is not properly controlled, it will roll or bounce away from the player who will have to spend time retrieving it before the exercise can be started again.
Recognising this problem, several soccer training devices have been designed to assist in this type of soccer practice. These devices all work by attaching a line to the ball, and either attaching the other end to the player (for example by a belt) or having the player hold the other end of the line whilst he or she is practising. In some of these training devices, the line is attached to the ball by placing the ball in a string bag attached to the end of the line.
Although such devices are commercially successful, they have significant disadvantages. Firstly, because the ball is tethered, it is not free to move in entirely the same way as an untethered ball. Secondly, the presence of a string bag around the ball means that the contact between the player's foot and the ball is distorted. Thirdly, there is a danger that the tether line may become caught around the player's legs or entangled with itself or with other objects.
Fourthly, if the ball is kicked hard, it can rebound and strike the player which is not always desirable.